Roof bow



FIG. 1 is a front plan view of a roof bow for a vehicle showing my new design;

FIG. 2 is an end view of the roof bow thereof; and,

FIG. 3 is a perspective view of the roof bow.

In the drawings, the broken lines depict portions of the design that form no part of the claimed design. 

The ornamental design for a roof bow, as shown and described. 